There may be nothing new under the sun when it comes to etching PCBs with UV light, but Heliosoph has brought finer control to a used face tanner he bought that now exposes his boards in ~50 seconds.
The original system allowed for exposure times from 1-99 minutes to be programmed in 1-minute increments. Heliosoph though it would be perfect as-is, but the lamp is so powerful that even one minute of exposure was too much. He hoped to find TTL when he opened the thing and was pleasantly surprised to discover a COP410L microcontroller and an MM5484 display driver. Unfortunately, the COP410L’s clock range is too small and he didn’t want to overclock it.
Heliosoph built a new board based on the ATMega328P with a salvaged 16×2 LCD, which he was able to easily integrate using the library that ships with the Arduino IDE. He then replaced the BT136 triac lamp switch with a solid state relay, conveniently isolating the electronics from mains power. He re-purposed the unit’s push buttons using the M2tklib, which supports a plethora of common menu functions.
If you need some help with the whole UV PCB etching process, you can’t go wrong with this tutorial from CNLohr.
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